Capybara

Range:
South America east of the Andes, from the northern edge of the continent down to as far south as the northern part of Argentina

Habitat:
Dense vegetation surrounding lakes, rivers, swamps, marshes, and ponds

Size:
Length: 39-51 in; Height: ~20 in; Weight: 59.4-173.8 lbs

Young:
Average litter size is 4.

Gestation:
Around 150 days.

Diet (wild):
Grazers (herbivore): grasses, aquatic plants, grains, melons, and squashes.

Diet (zoo):
Hay & herbivore pellets

Lifespan (wild):
8-10 years.

Lifespan (captivity):
8-12 years.

Status:
It is not listed, although it has disappeared from some areas, but is still common over most of the continent.

Threats:
Hunting, extermination, and habitat loss

Anatomy/Physiology:
They are reddish brown to greyish and are usually yellowish brown on the underside. They have almost no tail, they have short legs, short and rounded ears, and the muzzle is heavy. The toes are webbed and they have strong claws. Females are usually larger, but the male has a large scent gland on the top of its snout. They have a very efficient digestive system that enhances the amount of nutrition they get from their food. This involves extensive chewing and hindgut fermentation.

Social/Family units:
They are social and live in groups of about 20, but the basic unit is a family group. The units have one dominant adult male, several adult females with their own hierarchy, their offspring, and subordinate males that live on the edge of the group. Adult males that do not have a family unit may be solitary. Group sizes tend to be larger in more arid areas, and during drought several hundred individuals may aggregate around the remaining water holes.

Habits:
In the hottest part of the day they will wallow in shady, wet areas. They are semi-aquatic and love to be in the water.

Communication:
They make soft whimpering noises when contended. They can also produce a shrill, piercing whistle or a short grunting sound. They purr to show submissivness.

Defensive/Aggressive behavior:
When threatened, they flee in long leaps and will use the water as a shelter from danger.

Predators:
Anaconda, jaguars, ocelots, pumas, the harpy eagle, and humans

Locomotion:
Good swimmers, with both fore and hind feet webbed. They can swim with their eyes, ears, and nostrils out of the water, or completely submerged. Their normal gait is a slow walk, but they are able to take long leaps when in flight.

Activity:
Crepuscular

Interesting story/facts:
They are the largest rodents in the world. They have been able to thrive on cattle ranches. This is due to their safety from predators, the constant supply of water (even in droughts), and the grasses are periodically burned, increasing their quality. In some places the population numbers are higher on the ranches than they were before the land was developed.
Also, capybaras have been raised commercially on ranches. This form of ranching benefits the environment by preserving wetlands rather than draining them as would be done for cattle ranching.